1. Field of the Invention
The present invention relates to vibrating gyro devices that detect rotation by utilizing deformation of a piezoelectric substance in a direction perpendicular or substantially perpendicular to a main surface of the piezoelectric substance and deformation of the piezoelectric substance in a direction parallel or substantially parallel to a main surface of the piezoelectric substance, and also relates to methods for manufacturing such vibrating gyro devices.
2. Description of the Related Art
A vibrating gyro device that detects rotation includes, for example, a vibrating board to which a piezoelectric ceramic has been affixed or a vibrating board made of a piezoelectric single crystal, such as quartz, lithium niobate, or lithium tantalate, and detects the Coriolis force acting on the vibrator. Such vibrators have a variety of shapes including a tuning fork shape, a square-cross-section tuning bar shape, an equilateral-triangle-cross-section tuning bar shape, a circular tuning bar shape, and an H shape (see, for example, “Piezoelectric Vibrating Gyroscope”, Journal of the Acoustical Society of Japan Vol. 45 No. 5 pp. 402-408, 1989, “Piezoelectric Vibrating Gyroscope Angular Velocity Sensor,” IEICE Transactions Vol. J78-C-I pp. 547-556, February 1995, and “Electronic Mechanism Device Employing Lithium Niobate and Lithium Tantalate Piezoelectric Single Crystals” IEICE Transactions Vol. J87-C No. 2 pp. 216-224, February 2004 and JP Patent No. 3218702).
FIGS. 1A and 1B show the configuration of an example of a conventional vibrating gyro device.
This vibrating gyro device 101 includes a vibrating board 104, eight detection vibrators, and one driving vibrator. Each of the detection vibrators includes a detection electrode 102, a piezoelectric board 103, and a detection electrode 105. The driving vibrator includes a driving electrode 106, a piezoelectric board 107, and a driving electrode 108. The driving vibrator excites bending vibration in the vibrating board 104 in a direction perpendicular to a main surface of the vibrating board 104. In each pair of the eight detection vibrators arranged on either side of a corresponding one of two perpendicular detection axes (X axis and Y axis) of the vibrating gyro device 101, an output signal is excited by a difference between outputs thereof corresponding to the Coriolis force of rotation about the detection axis that is interposed between the pair of detection vibrators.
This type of vibrating gyro device, which is capable of detecting rotation about each of a plurality of axes of rotation, is used in automobile navigation systems, camera shake-compensation circuits, remote controllers of game consoles, mobile telephones and other suitable devices. In these applications, it is desirable to reduce the size of vibrating gyro devices to be less than that of conventional vibrating gyro devices.
In the tuning-fork-shaped and tuning-bar-shaped vibrating gyro devices described in “Piezoelectric Vibrating Gyroscope”, Journal of the Acoustical Society of Japan Vol. 45 No. 5 pp. 402-408, 1989, “Piezoelectric Vibrating Gyroscope Angular Velocity Sensor,” IEICE Transactions Vol. J78-C-1 pp. 547-556, February 1995, “Electronic Mechanism Device Employing Lithium Niobate and Lithium Tantalate Piezoelectric Single Crystals” IEICE Transactions Vol. J87-C No. 2 pp. 216-224, February 2004 and JP Patent No. 3218702), for each vibrator, only a single detection axis can be provided and a plurality of vibrators are required to provide a plurality of detection axes, which is not suitable to reduce the size of the device. In particular, in a configuration in which electrodes are not only formed on the front and back but also on the side surfaces of a vibrator, since the forming of electrodes and wiring therefor on the side surfaces is difficult when the size of the vibrator is reduced, there are limits on how thin the vibrator can be made.
A disk-shaped vibrating gyro device described in JP Patent No. 3218702 can detect rotation about two orthogonal axes, but the thinner the vibrating board is made, the lower the rigidity of the board becomes and, therefore, as the amount that the vibrating board bends under its own weight increases, the deviation from the ideal vibration mode increases. Furthermore, there is a risk of the vibrating board bending and thereby coming into contact with a supporting body and, therefore, it is necessary to provide a larger vibration space. Therefore, there are limits to how thin the vibrating board can be made.